FIG. 1 illustrates a block diagram of a conventional ‘load-following’ engine power determination architecture 10 for a hybrid electric vehicle. In the conventional architecture 10, an engine power command 12 is determined as the sum of a driver power command 14 and a battery power command 16. As such, in the conventional architecture 10, the engine directly responds to any change of the driver power command 14.
Accordingly, in real-world driving, any chaotic and aggressive driver power command 14 can easily generate a perturbation of the engine power command 12. The perturbation can be reflected as fast-fluctuations and dithering in the engine power command 12. Such transients may adversely affect the engine combustion efficiency and cost extra transient fuel. Further, many engine control parameters are ‘predicatively’ scheduled based on the rate of change of engine power command 12. Therefore, engine power disturbances may cause other non-optimum engine settings and worsen fuel/air errors. Even if the A/F ratio can be kept within a moderate narrow range, the integration effect of the fuel enrichments caused by more frequently occurring transients can be magnified and accumulated up to a considerable level of fuel losses.